1964 – Theodore L. Bailey joined Preston-Patterson as a principal. Bailey brought the business from Francis A. Donaldson Co., a firm that was formed in 1866 and that Bailey acquired in 1956. Richard M. Patterson, the son of Richard D. Patterson also joined Preston-Patterson.

1983 – John and Stephen Patterson, two of Richard’s sons joined Preston-Patterson.

1994 – Stuart Patterson, the youngest son of Richard joined Preston-Patterson.